Measuring the loudest calls in nature
Biologists at the University of Massachusetts Amherst set out to find which birds are loudest. Jeff Podos and his former graduate student Joao Menezes recorded 123 species in Brazil and Massachusetts. Two birds stood out.
The bare-throated bellbird, which lives in the Amazon, produced calls of about 131 peak decibels. The red-legged seriema, found across a wide part of eastern South America, topped 120 decibels. Both are louder than a chainsaw, a jackhammer or a jet plane taking off.
Bigger bodies and wider beaks
The team found a 58-decibel range across species. At the quiet end, hummingbirds called at about 64 decibels, roughly the level of a normal conversation. Louder calls went with larger bodies and wider beak openings, the study found.
Other ideas did not hold up. The researchers looked for a link between volume and habitat, flight ability or mating system, and found none that was clear. The red-legged seriema was a surprise for exactly that reason. It lives in open country and sings in duets with a partner, so neither dense forest nor competition for mates explains why it is so loud.
What the finding adds
The work was published in the journal Evolution. It gives researchers a baseline for comparing how and why animals use sound. Loud calls cost energy and can attract predators, so species that invest in them usually gain something in return.
The seriema's duets may be about holding territory or staying in contact across long distances. For now that is a guess. The team says the next step is to test how far the calls travel and how other birds respond to them.